1. Field of the Invention
The present invention relates to DC power supplies, and more particularly, but not byway of limitation, to a power supply and control circuit incorporating an improved design for supplying a variable DC voltage to a device.
2. History of the Prior Art
Power supplies are widely used in industrial and commercial applications to provide DC potentials for electrical and electronic equipment. Power supplies are generally included as an integral part of equipment which requires DC potentials, but also exist as self-contained units. The primary function of any power supply is to convert AC power to useful DC potentials. This conversion process requires at least two and usually three operations which include rectification, filtering and regulation or control.
Many present designs use high-frequency switching power supplies or use transformers to supply the appropriate voltage or voltages. Switching power supplies tend to be expensive and run at a high frequencies possibly causing electro-magnetic interference or leakage current problems. Transformers tend to be heavy, bulky and expensive. In many applications, special transformers must be designed which increases the cost.
Two applications, among others, of the present invention include providing power to and control of the speed of DC motors, providing power for the charging of batteries, etc. DC motors would benefit from the present invention through more efficient power application, lighter weight, lower cost and the absence of the need for high frequency pulse width modulation (PWM) control. A variable voltage output would be provided to the DC motor depending on the voltage needed to acquire the desired motor speed.
Batteries and the charging thereof would benefit because the present invention would provide a smaller, lighter weight and reduced cost alternative to transformer-based linear power supplies or high frequency switching power supplies. Current capabilities of more than ten amps DC can be achieved for charging by the present invention without the cost and weight required by a transformer rated as such a high current. In addition, the efficiency of the present invention is greater than that obtained using a transformer.
The present invention provides an improvement over the prior art by providing a smooth DC voltage for use with DC motors and the charging of batteries and eliminates the use of bulky inductors or transformers, does not operate at high frequencies typical of switching power supplies and maintains a low part count.